The present invention relates to compact electronic equipment which uses a paper-like cell as a power source.
Various types of compact card- or sheet-like electronic equipment such as electronic calculators having a very small thickness of up to about 1 mm have been recently developed. Compact electronic equipment of this type generally has a solar cell having a thickness of about 0.2 mm as a power source cell.
However, with compact electronic equipment having a memory and/or timepiece function, if a solar cell is used as a power source cell, the solar cell cannot receive a sufficient amount of light at times such as at nighttime. The power source voltage cannot then be supplied, and the stored memory contents are lost or the timepiece function cannot be obtained. In view of this problem, compact electronic equipment of this type must have a primary cell.
Such primary cells include button-shaped cells such as a mercury cell, a silver oxide cell, or a lithium cell. A button-shaped cell has a considerably large thickness as compared with a solar cell. For example, the thinnest button-shaped lithium cell available on the market today has a thickness of 1.6 mm. Compact electronic equipment having a memory and/or timepiece function must use such a button-shaped cell and therefore has a considerably larger thickness than compact electronic equipment using a solar cell.